As far as I know, this is incorrect information. Later versions of the runtime engine DO NOT support executables built from earlier versions of LabVIEW. Rather, there has always been a one-to-one correspondence between the executable version and the RTE. And yes, multiple RTEs can coexist in a given installation. I've got three (5.1, 6.0.2, 6.1) on several test stations on our factory floor.
Regards,
Dave
David Boyd
Sr. Test Engineer
Abbott Labs
(lapsed) Certified LabVIEW Developer